Pulmonary oedema is a very frequent and extremely important disease. Its essential and primary symptom is the infiltration of the parenchyma with a serous fluid, which is obvious even from an external inspection, and much more so on examining the interior of the viscus, which pours forth a serous fluid when a section is made into it. The serum, however, does not vary only in regard to its quantity (that is to say, not only are there differences in the degrees of the oedema), but it likewise presents many differences in relation to its properties.

In order to understand the importance of pulmonary oedema under all conditions, it is necessary for us to direct attention to the information which we have acquired from clinical observation, and from careful examination and experimental investigation of the dead body in relation to the seat of the serous effusion. We thus ascertain that the serum is effused into the cavities of the air-cells, where it accumulates, either alone or mixed with varying quantities of air, according to circumstances. From hence it flows in greater or less quantity, either mixed with air and frothy (as bronchial foam), or unmixed with air, into the bronchial tubes. The walls of the air-cells and the interstitial tissue are also more or less saturated and infiltrated with serum, but the true seat of the fluid which so often escapes in astonishing quantities from the cut surface of the parenchyma of an ©edematous lung is in the air-cells and the bronchial canals.

Pulmonary oedema occurs both in an acute and in a chronic form, and between these extremes there are many transition stages presenting mere shades of difference. In acute oedema the lung appears swollen, does not collapse, feels puffy, and when we press it with the finger we detect a fluid which escapes with a crackling noise; its elasticity is only slightly diminished, so that scarcely any perceptible pitting remains after the pressure; it is of a pale reddish colour, very pale and deficient in blood when anaemia is present, and more or less red and congested if there be hyperemia; the serum which is effused from the cut surface is mixed with much air, which renders it frothy, and is usually of a pale red color; but in oedema arising from prolonged stasis and simultaneous decomposition of the blood, it is red and discolored, having an icteric tint. The parenchyma is softer than usual, very moist, singularly yielding, and easily torn.

If the oedema lasts for a longer time, the pulmonary tissue gradually loses its elasticity, the lung pits more distinctly on pressure, becomes paler, assumes a faded, dirty gray color, and becomes opaque and dull; the air is gradually pressed out of it; it crepitates less, when cut; and the serum is less frothy, gradually loses its color, and becomes clear and limpid. The parenchyma becomes gradually infiltrated with serum, the walls of the air-cells and the interstitial tissue become swollen, and hence the lung becomes denser and more resistant.

Finally, in cases where chronic oedema has been very fully developed from its commencement, the lung appears pale, of a dirty gray color, anaemic, not swollen, but heavy, dense, and resistant, pitting on pressure and no longer crepitating; a grayish or somewhat greenish serum unmixed with air flows from the cut surface. Dropsical accumulation in the pleural sac is almost always simultaneously present.

Oedema Of The Lungs

Oedema Of The Lungs, like acute oedema of the glottis, is often very rapidly developed; from an active hyperaemia or a passive or mechanical stasis, it quickly reaches a high degree of intensity, extends simultaneously over both lungs, and in a short time causes death by suffocation. This is frequently the cause of the suffocation of adults and of new-born children, and is often combined with hyperaemia and serous effusion within the cavity of the cranium. The dead body usually presents the same appearances as those which we have described as occurring in pulmonary apoplexy; the lungs in particular exhibit oedema, and a frothy serous fluid is accumulated in the bronchial passages, which is frequently seen as a thick, white, or whitish-red froth, at the oral and nasal cavities. It may also be developed as a consequence of acute or chronic bronchial catarrh, or of exudative processes (croup) on the tracheal and bronchial mucous membranes; it is a constant symptom in acute pulmonary tuberculosis, in acute decompositions of the blood and after the retrogression of erysipelas, scarlatina, variola, rheumatism, miliaria, etc. In the form of more or less developed acute oedema it accompanies the various stages of pneumonia and the metastases: and is associated with haemoptoic in-farctus, with pulmonary cancer, and especially with pulmonary tuberculosis. Lastly, it appears as a consequence of cerebral diseases, of general anaemia and tabes, and occurs towards the end of almost all chronic diseases.

Chronic oedema, moreover, exists with general dropsy, with dropsy of the great serous sacs, with chronic diseases of the heart and great vessels, etc. It is rarely an idiopathic and independent disease.

The extent of oedema is various; the very acute and rapidly fatal oedema generally attacks both lungs almost equally; in other cases it is limited to individual portions of them. The oedema in cases of pneumonia commonly affects the circumference of the inflamed part; that which occurs as a consequence of chronic diseases, for the most part, attacks the posterior and inferior parts of the lungs, which are most exposed to the influence of gravitation.